β2 adrenergic agonists and cholinergic muscarinic antagonists are well-established therapeutic agents for the treatment of obstructive respiratory diseases such as COPD and Asthma. Currently used inhaled β2 agonists include both short acting agents such as salbutamol (q.i.d.), and terbutaline (t.i.d) and longer acting agents such as salmeterol, and formoterol (b.i.d.) and produce bronchodilation via stimulation of adrenergic receptors on airway smooth muscle. Inhaled Muscarinic antagonists in clinical use include the short acting ipratropium bromide (q.i.d.), oxitropium bromide (q.i.d) and the long acting tiotropium (q.d.). Muscarinic antagonists produce bronchodilation by inhibiting the cholinergic tone of airways primarily by antagonising the action of acetylcholine on muscarinic receptors present on airway smooth muscle. A number of published studies have demonstrated that the combined administration of inhaled β2agonists with inhaled muscarinic antagonists (whether short or long acting) to patients with obstructive lung disease results in superior improvements in lung function, symptoms and quality of life measures compared to patients receiving either single class of agent alone. Studies to date have been restricted to combination studies with single pharmacology agents, however combination of both pharmacologies within a single molecule would be desirable as this could yield increased bronchodilator efficacy with similar therapeutic index to the single agents or similar efficacy with superior therapeutic index. In addition, combining both pharmacologies in a single molecule would allow the potential for combination with anti-inflammatory agents thus giving a triple therapy from a single inhaler.